I am a first time 3D designer and printer. I am working on printing a teacup, and have been refining the design after getting feedback here and at Ponoko.com. I am getting close to printing this project, but one of the support staff at Ponoko, after reviewing my STL file, recommended I make the teacup all "one skin" instead of having the "overlapping geometry" on the base of the cup. So my question is this, what does "overlapping geometry" mean in terms of 3D design/printing, and how do I remove it from this design? I have attached my STL file.